1. Field Of The Invention
The present invention relates to an apparatus for recording and reproducing a digital video signal, and particularly to an apparatus for recording and reproducing digital video signals of video images of plural different video systems.
2. Description Of The Related Art
In an apparatus for recording and reproducing a digital video signal, first, one frame of a video image is divided into a plurality of image blocks. Second, the known DCT block (discrete cosine transform block) composed of 64 pixels (8 pixel.times.4 lines.times.2 fields) is defined as a unit of image. One image block comprises one DCT block representing a color difference signal (R-Y), one DCT block representing another color difference signal (B-Y) and four DCT blocks representing a luminance signal Y. Therefore, in the PAL system (hereinafter referred to as 625/50 system) for example, one frame of a video image is divided into 45 image blocks in the horizontal direction and 36 image blocks in the vertical direction. Consequently, one frame of the video image is divided into 1620 image blocks. Data of each image block divided as mentioned above is converted into coded data. A main component of the coded data of each image block is stored in one synchronizing block (hereinafter is referred to as SYNC block).
Subsequently, one frame of the video image is divided into 12 sections in the vertical direction. The SYNC block data having the coded data of the image blocks in each section are recorded on one video track of a magnetic tape. In the recording operation, the order of arrangement of the SYNC block data to be recorded on one video track is set so that the image blocks corresponding to those SYNC block data are substantially arranged at neighboring locations on an original video image. The video data of one frame divided into 12 sections are recorded in 12 video tracks.
In the NTSC system (hereinafter is referred to as 525/60 system), one frame of a video image is divided into 22.5 image blocks in the horizontal direction and 60 image blocks in the vertical direction, and consequently, one frame is divided into 1350 image blocks. The data of each image block is converted into coded data, and is stored in a corresponding SYNC block. Subsequently, one frame of the video image is divided into 10 sections in the vertical direction. A similar operation to that of the 625/50 system is applied to the data of the image blocks of each section. The SYNC block data having the coded data of the image blocks in each section are recorded in one track of the magnetic tape. Consequently, the video data of one frame is recorded on 10 video tracks.
In the above-mentioned recording methods, the signal processing method in the 625/50 system is similar to the signal processing method in the 525/60 system, and a common circuit is usable for both the systems. More-over, during high speed reproduction of the recorded data, the video images reproduced from the video data of one video track are substantially arranged at neighboring locations on the reproduced video image.
In the conventional apparatus for recording and reproducing of the digital video signal, if the number of pixel per one frame is not greatly different from each other between two separate systems, such as the 525/60 system and the 625/50 system, the same signal processing circuit is usable for both the systems. However, for example, the number of pixel per one frame in a video system is several times the number of pixel per one frame in the 625/50 system, such as the HDTV system versus 625/50 system, for example, it is difficult to use the same signal processing circuit.